Results 1  10
of
44
Optimality of diagonalization of multihop MIMO relays
 IEEE Trans. Wireless Commun
"... Abstract—For a twohop linear nonregenerative multipleinput multipleoutput (MIMO) relay system where the direct link between source and destination is negligible, the optimal design of the source and relay matrices has been recently established for a broad class of objective functions. The optima ..."
Abstract

Cited by 45 (29 self)
 Add to MetaCart
(Show Context)
Abstract—For a twohop linear nonregenerative multipleinput multipleoutput (MIMO) relay system where the direct link between source and destination is negligible, the optimal design of the source and relay matrices has been recently established for a broad class of objective functions. The optimal source and relay matrices jointly diagonalize the MIMO relay system into a set of parallel scalar channels. In this paper, we show that this diagonalization is also optimal for a multihop MIMO relay system with any number of hops, which is a further generalization of several previously established results. Specifically, for Schurconcave objective functions, the optimal source precoding matrix, the optimal relay amplifying matrices and the optimal receiving matrix jointly diagonalize the multihop MIMO relay channel. And for Schurconvex objectives, such joint diagonalization along with a rotation of the source precoding matrix is also shown to be optimal. We also analyze the system performance when each node has the same transmission power budget and the same asymptotically large number of antennas. The asymptotic analysis shows a good agreement with numerical results under a finite number of antennas. Index Terms—MIMO relay network, multihop relay, linear nonregenerative relay, majorization.
1 Protocol Design and Throughput Analysis for Multiuser Cognitive Cooperative Systems
, 2009
"... This paper deals with protocol design for cognitive cooperative systems with many secondary users. In contrast with previous cognitive configurations, the channel model considered assumes a cluster of secondary users which perform both a sensing process for transmitting opportunities and can relay d ..."
Abstract

Cited by 28 (3 self)
 Add to MetaCart
This paper deals with protocol design for cognitive cooperative systems with many secondary users. In contrast with previous cognitive configurations, the channel model considered assumes a cluster of secondary users which perform both a sensing process for transmitting opportunities and can relay data for the primary user. Appropriate relaying improves the throughput of the primary users and can increase the transmission opportunities for the cognitive users. Based on different multiaccess protocols, the schemes investigated enable relaying either between the primary user and a selected secondary user or between two selected secondary users. This collaboration can be a simple distributed multipleinput singleoutput transmission of the primary data or a simultaneous transmission of primary and secondary data using dirtypaper coding (DPC). The parametrization of DPC as well as its combination with opportunistic relay selection yields an interesting tradeoff between the primary and the secondary performance which is investigated by theoretical and simulation results under the perspective of a desired primary throughput. The proposed protocols are studied from a networking point of view and the stable throughput for primary and secondary users is derived based on the principles of queueing theory. Index Terms analysis.
Optimal linear nonregenerative multihop MIMO relays with MMSEDFE receiver at the destination
 IEEE Trans. Wireless Commun
, 2010
"... Abstract—In this paper, we study multihop nonregenerative multipleinput multipleoutput (MIMO) relay communications with any number of hops. We design the optimal source precoding matrix and the optimal relay amplifying matrices for such relay network where a nonlinear minimal meansquared error ..."
Abstract

Cited by 23 (17 self)
 Add to MetaCart
(Show Context)
Abstract—In this paper, we study multihop nonregenerative multipleinput multipleoutput (MIMO) relay communications with any number of hops. We design the optimal source precoding matrix and the optimal relay amplifying matrices for such relay network where a nonlinear minimal meansquared error (MMSE)decision feedback equalizer (DFE) is used at the destination node. We first derive the structure of the optimal source and relay matrices. Then based on the link between most commonly used MIMO system design objectives and the diagonal elements of the MSE matrix, we classify the objective functions into two categories: Schurconvex and Schurconcave composite objective functions. We show that when the composite objective function is Schurconvex, the MMSEDFE receiver together with the optimal source and relay matrices enable an arbitrary number of source symbols to be transmitted at one time, and yield a significantly improved BER performance compared with nonregenerative MIMO relay systems using linear receivers at the destination. We also show that for Schurconcave composite objective functions, the optimal source and relay matrices, and the optimal feedforward matrix at the destination node jointly diagonalize the multihop MIMO relay channel, and thus in such case, the nonlinear MMSEDFE receiver is essentially equivalent to a linear MMSE receiver. Index Terms—MIMO relay network, multihop relay, MMSE, DFE, nonregenerative relay, majorization.
Analog network coding in the highsnr regime
 in Proc. IEEE Wireless Network Coding Workshop
"... Abstract—A node performing analog network coding simply forwards a signal it receives over a wireless channel. This allows for a (noisy) linear combination of signals simultaneously sent from multiple sources to be forwarded in the network. As such, analog network coding extends the idea of network ..."
Abstract

Cited by 20 (6 self)
 Add to MetaCart
(Show Context)
Abstract—A node performing analog network coding simply forwards a signal it receives over a wireless channel. This allows for a (noisy) linear combination of signals simultaneously sent from multiple sources to be forwarded in the network. As such, analog network coding extends the idea of network coding to wireless networks. However, the analog network coding performance is limited by propagated noise, and we expect this strategy to perform well only in high SNR. In this paper, we formalize this intuition and determine highSNR conditions under which analog network coding approaches capacity in a layered relay network. By relating the received SNR at the nodes with the propagated noise, we determine the rate achievable with analog network coding. In particular, when all the received powers are lower bounded by 1/δ, the propagated noise power in a network with L layers is of the order Lδ. The result demonstrates that the analog network coding approaches the cutset bound as the received powers at relays increase. As all powers in the network increase, the analog network coding rate is within a constant gap from the upper bound. The gap depends on number of nodes. We further demonstrate by an example that analog network coding can perform close to sumcapacity also in the multicast case. I.
A tutorial on the optimization of amplifyandforward MIMO relay systems
 IEEE J. Select. Areas Commun
, 2012
"... Abstract—The remarkable promise of multipleinput multipleoutput (MIMO) wireless channels has motivated an intense research activity to characterize the theoretical and practical issues associated with the design of transmit (source) and receive (destination) processing matrices under different op ..."
Abstract

Cited by 19 (7 self)
 Add to MetaCart
(Show Context)
Abstract—The remarkable promise of multipleinput multipleoutput (MIMO) wireless channels has motivated an intense research activity to characterize the theoretical and practical issues associated with the design of transmit (source) and receive (destination) processing matrices under different operating conditions. This activity was primarily focused on pointtopoint (singlehop) communications but more recently there has been an extensive work on twohop or multihop settings in which single or multiple relays are used to deliver the information from the source to the destination. The aim of this tutorial is to provide an uptodate overview of the fundamental results and practical implementation issues in designing amplifyandforward MIMO relay systems. Index Terms—Tutorial, MIMO, optimization, transceiver design, amplifyandforward, nonregenerative relay, power allocation, majorization theory, qualityofservice requirements, singlehop, twohop, multihop, oneway, twoway, multiple relays, perfect channel state information, robust design. I.
Asymptotic capacity and optimal precoding strategy of multilevel precode
 IEEE Trans. Inform. Theory
"... Abstract — We analyze a multilevel MIMO relaying system where a multipleantenna transmitter sends data to a multipleantenna receiver through several relay levels, also equipped with multiple antennas. Assuming correlated fading in each hop, each relay receives a faded version of the signal transmi ..."
Abstract

Cited by 13 (3 self)
 Add to MetaCart
(Show Context)
Abstract — We analyze a multilevel MIMO relaying system where a multipleantenna transmitter sends data to a multipleantenna receiver through several relay levels, also equipped with multiple antennas. Assuming correlated fading in each hop, each relay receives a faded version of the signal transmitted by the previous level, performs precoding on the received signal and retransmits it to the next level. Using free probability theory and assuming that the noise power at the relay levels but not at the receiver is negligible, a closedform expression of the endtoend asymptotic instantaneous mutual information is derived as the number of antennas in all levels grow large with the same rate. This asymptotic expression is shown to be independent from the channel realizations, to only depend on the channel statistics and to also serve as the asymptotic value of the endtoend average mutual information. We also provide the optimal singular vectors of the precoding matrices that maximize the asymptotic mutual information: the optimal transmit directions represented by the singular vectors of the precoding matrices are aligned on the eigenvectors of the channel correlation matrices, therefore they can be determined only using the known statistics of the channel matrices and do not depend on a particular channel realization. I.
Multihop nonregenerative MIMO relays: QoS considerations
 IEEE Trans. Signal Process
, 2011
"... tipleoutput (MIMO) relay communication systems, the optimal source precoding matrix and the optimal relay amplifying matrices have been recently established for a broad class of objective functions subjecting to the transmission power constraint at each node. However, existing works do not conside ..."
Abstract

Cited by 10 (7 self)
 Add to MetaCart
tipleoutput (MIMO) relay communication systems, the optimal source precoding matrix and the optimal relay amplifying matrices have been recently established for a broad class of objective functions subjecting to the transmission power constraint at each node. However, existing works do not consider any qualityofservice (QoS) constraints, which are important in practical communication systems. In this paper, we derive the optimal source and relay matrices of a multihop MIMO relay system that guarantee the predetermined QoS criteria be attained with the minimal total transmission power. In particular, we consider two types of receivers at the destination node: the linear minimal meansquared error (MMSE) receiver and the nonlinear decision feedback equalizer (DFE) based on the MMSE criterion. We show that for both types of receivers, the solution to the original optimization problem can be upperbounded by using a successive geometric programming (GP) approach and lowerbounded by utilizing a dual decomposition technique. Simulation results show that both bounds are tight, and to obtain the same QoS, the MIMO relay system using the nonlinear MMSEDFE receiver requires substantially less total transmission power than the linear MMSE receiverbased system. Index Terms—Linear nonregenerative relay, majorization, minimal meansquared error (MMSE), multihop relay, multipleinput multipleoutput (MIMO) relay, QoS. I.
Multihop cooperative wireless networks: Diversity multiplexing tradeoff and optimal code design
 in Proc. Inf. Theory Appl. Worksh., UCSD
, 2008
"... Abstract — In this paper, we consider singlesource, singlesink (ssss) multihop relay networks, with slowfading Rayleigh links and singleantenna relay nodes operating under the halfduplex constraint. We present protocols and codes to achieve the optimal diversitymultiplexing tradeoff (DMT) of ..."
Abstract

Cited by 10 (5 self)
 Add to MetaCart
(Show Context)
Abstract — In this paper, we consider singlesource, singlesink (ssss) multihop relay networks, with slowfading Rayleigh links and singleantenna relay nodes operating under the halfduplex constraint. We present protocols and codes to achieve the optimal diversitymultiplexing tradeoff (DMT) of two classes of networks. Networks belonging to the first class can be viewed as the union of K nodedisjoint parallel paths, each of length> 1, labeled here as KPP networks. The results are extended to variants including KPP(I) networks which permit causal interference between paths and KPP(D) networks which posses a direct link from source to sink. The second class is comprised of layered networks in which each layer is fully connected. We also draw some results for more general networks. For an arbitrary network with multiple flows, we show that the maximum achievable diversity gain for each flow is equal to the corresponding mincut and present a simple amplifyandforward (AF) scheme for achieving the same. For arbitrary ssss directed networks with fullduplex relays, we prove that a linear tradeoff between maximum diversity and maximum multiplexing gain is achievable using an AF protocol. Explicit codes with short blocklengths based on cyclic division algebras are given for all the proposed protocols. Two key implications of the results in the paper are that the halfduplex constraint does not necessarily entail rate loss by a factor of two as previously believed and that simple AF protocols are often sufficient to attain the best possible DMT. I.
Code Design for Multihop Wireless Relay Networks
, 2008
"... We consider a wireless relay network, where a transmitter node communicates with a receiver node with the help of relay nodes. Most coding strategies considered so far assume that the relay nodes are used for one hop. We address the problem of code design when relay nodes may be used for more than o ..."
Abstract

Cited by 10 (0 self)
 Add to MetaCart
We consider a wireless relay network, where a transmitter node communicates with a receiver node with the help of relay nodes. Most coding strategies considered so far assume that the relay nodes are used for one hop. We address the problem of code design when relay nodes may be used for more than one hop. We consider as a protocol a more elaborated version of amplifyandforward, called distributed spacetime coding, where the relay nodes multiply their received signal with a unitary matrix, in such a way that the receiver senses a spacetime code. We first show that in this scenario, as expected, the socalled fulldiversity condition holds, namely, the codebook of distributed spacetime codewords has to be designed such that the difference of any two distinct codewords is full rank. We then compute the diversity of the channel, and show that it is given by the minimum number of relay nodes among the hops. We finally give a systematic way of building fully diverse codebooks and provide simulation results for their performance.
Asymptotic Capacity and Optimal Precoding in MIMO MultiHop Relay Networks
, 906
"... A multihop relaying system is analyzed where data sent by a multiantenna source is relayed by successive multiantenna relays until it reaches a multiantenna destination. Assuming correlated fading at each hop, each relay receives a faded version of the signal from the previous level, performs li ..."
Abstract

Cited by 8 (1 self)
 Add to MetaCart
(Show Context)
A multihop relaying system is analyzed where data sent by a multiantenna source is relayed by successive multiantenna relays until it reaches a multiantenna destination. Assuming correlated fading at each hop, each relay receives a faded version of the signal from the previous level, performs linear precoding and retransmits it to the next level. Using free probability theory and assuming that the noise power at relaying levels — but not at destination — is negligible, the closedform expression of the asymptotic instantaneous endtoend mutual information is derived as the number of antennas at all levels grows large. The soobtained deterministic expression is independent from the channel realizations while depending only on channel statistics. Moreover, it also serves as the asymptotic value of the average endtoend mutual information. The optimal singular vectors of the precoding matrices that maximize the average mutual information with finite number of antennas at all levels are also provided. It turns out that the optimal precoding singular vectors are aligned to the eigenvectors of the channel correlation matrices. Thus they can be determined using only the known channel statistics. As the optimal precoding singular vectors are independent from the system size, they are also optimal in the asymptotic regime.